Downhole cable protection device

ABSTRACT

A device for an underground well, typically a petroleum well ( 1 ), wherein, in the uncased inflow portion ( 2, 4, 6 ) of the well, there is placed an inflow pipe, possibly in the form of a strainer pipe ( 8 ) comprising a strainer/perforated outer mantle ( 16 ), a main pipe ( 12 ) located within and a number of preferably axial spacer strips ( 18 ) spaced apart about the external periphery of the main pipe and arranged to support the strainer mantle ( 16 ), whereby there are, in the space defined by the strainer mantle ( 16 ) and the main pipe ( 12 ), channels  20  between the spacers ( 18 ), and in one or more of the channels  20 , there extends at least one cable, pipe or hose ( 34, 38 ).

CROSS REFERENCE TO RELATED APPLICATION

The present application is the U.S. national stage application ofInternational Application PCT/NO02/00132, filed Apr. 5, 2002, whichinternational application was published on Oct. 17, 2002 asInternational Publication WO 02/081862. The International Applicationclaims priority of Norwegian Patent Application 20011808, filed Apr. 10,2001.

BACKGROUND OF THE INVENTION

This invention relates to a device which forms a protected passage forcommunication cables, pipes or hoses in the well fluid inflow portion ofproduction tubing in wells of the kind used in the recovery ofpetroleum.

In recent years, in particular when horizontal wells are used, it hasbecome usual to use the so-called “open hole” technique. The techniqueinvolves that in a portion of the well, typically in one or more of thepetroleum-producing zones of the reservoir, no casing is set. Thus, whenthe production tubing is to be run, it must be moved into and through anopen well bore, within which it lies slidingly against the wellformation. To prevent sand from the formation from entering togetherwith the inflowing well fluid, and to support the formation wall andthus prevent the well bore from collapsing, it is common to setso-called strainer pipes in the petroleum-producing zones of thereservoir. In their outer jacket, the strainer pipes are provided withthrough openings in the form of fine bores or slots designed to admitwell fluid but prevent formation sand from reaching the productiontubing located within.

The development of the production technique in question has resulted inthe discovery of an increasing requirement for using downhole sensorsand actuators. Sensors are used, for example, for measuring one or moreof the physical properties of the well fluid, whereas actuators may beused, for example, for choking well fluid from one or more of the zonesof the reservoir. Communication between such downhole equipment and thesurface is normally accomplished by means of electrical cables, whereasenergy is supplied by means of electrical wires and/or hydraulic pipe orhose connections.

According to known technique, cables and pipes or hoses of the kind inquestion are placed in protective channels arranged for the purposeexternally on the strainer pipe. It is obvious that when productiontubing is being run, as the strainer pipes are subjected to displacementand rotation against the uncased formation, such protective channels aresubjected to huge mechanical loads. Experience goes to show that duringthe running operation damage will occur, to a considerable extent, onthese protective channels and the cables, pipes or hoses carried insidethe channels.

SUMMARY OF THE INVENTION

The invention has as its object to remedy the drawbacks of knowntechnique.

The object is achieved according to the invention through the featuresspecified in the description below and in the following claims.

A strainer pipe normally comprises an external, relatively thin-walledstrainer mantle and an internal, relatively strong perforatedload-carrying main pipe. The strainer mantle, which may be constructedfrom strainer wire, is supported concentrically by spacers, possibly inthe form of a number of longitudinal spacer rails spaced along theperiphery of the production tubing. The spacer rails are thus within anannular space between the strainer mantle and the main pipe.

During production well fluid enters through the openings of the strainermantle, through the annular space along the spacer rails and furtherthrough the perforations of the main pipe into the cavity of the mainpipe, after which the fluid flows to the surface through the productiontubing of the well.

To avoid the above-mentioned drawbacks of the known technique, cablesand hydraulic connections are placed in one or more longitudinal pipespresent in the annular space between the strainer mantle and the mainpipe. In such a solution the protective devices of cables and hydraulicconnections are subjected to minimal mechanical load, while at the sametime they reduce the flow area available for well fluid only to aninsignificant degree.

It is common to join together several strainer pipes which may form alength corresponding to the length of the producing zone of thereservoir. The annular space of each of the strainer pipes may beconnected to the annulus of the adjacent pipe by means of sleeves of akind known in itself, wherein the sleeves may be provided with externalopenings.

In some applications cables and hydraulic connections may be placed insaid annular space without the use of longitudinal pipes.

The device is also well suited for use in wells provided with a cementedand perforated liner.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following will be described a non-limiting example of a preferredembodiment which is visualized in the accompanying drawings, in which:

FIG. 1 shows schematically a petroleum well comprising an uncased wellpart, in which there are placed several downhole sensors and actuators,communicating with the surface through cables, pipes or hoses;

FIG. 2 shows a sectional view of a strainer pipe, in which there are, inthe annular space between the strainer mantle and the main pipe and inaddition to spacer rails, a number of passage pipes for cables, pipes orhoses;

FIG. 3 shows, partially in section, a side view of a strainer pipe whichis placed in an uncased formation and in which the strainer mantle isformed by a spun strainer wire;

FIG. 4 shows, partially in section, a side view of a strainer pipe whichis placed in an uncased formation and in which the strainer mantle isformed by a slotted pipe; and

FIG. 5 shows, partially in section, a side view of a perforated pipeplaced in an uncased formation, but the construction of the pipeotherwise exhibiting the same features as those shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings the reference numeral 1 identifies a petroleum well,there being placed, in the uncased petroleum-producing zones 2, 4, 6 ofthe well 1, a number of interconnected strainer pipes 8. Well fluidflows from the well 1 to the surface through a production tubing 10which is connected to the central main pipe 12 of the strainer pipe 8.The production tubing 8 extends through the casing 14 of the well 1.

In a preferred embodiment, the strainer pipe 8 comprises besides themain pipe 12, a strainer mantle 16 and a number of continuous or slottedspacer strips 18 spaced apart about the periphery of the main pipe 12and arranged to support the strainer mantle 16. In the annular spacebetween the strainer mantle 16 and the main pipe 12 there are, dependingon the number of spacer strips 18, a number of longitudinal channels 20,through which well fluid is flowing on its way from the slots 22 of thestrainer mantle 16 to the perforations 24 of the main pipe. The slots 22may be formed by means of, for example, a spun strainer wire 26 or aslotted mantle pipe 28.

It is common to fill the annulus formed between the uncased well portionand petroleum producing zones 2, 4, 6 with gravel 30 with the aim ofcontributing to the prevention of sand entrance and formation damage.

The well in FIG. 1 is provided with a number of sensors 32 communicatingwith the surface through a cable 34, and a number of actuators 36supplied with hydraulic or electrical energy through pipes, cables orhoses 38. In the well portion where a strainer pipe 8 is used, the cable34 and the pipes or hoses 38 extend through fluid tight protective pipes40 located in one or more of the channels 20, whereas in the upperportion of the well 1 they extend through the annulus formed between thecasing 12 and the production tubing 10 up to the surface. The protectivepipe 40 may possibly replace a spacer rail 18.

In another embodiment, essentially based on the technique describedabove, the strainer pipe 8 is provided with a perforated mantle pipe 42,see FIG. 5.

By placing the protective pipes 40 in the channels 20, the protectivepipes 40 are only exceptionally subjected to mechanical loads, wherebywires, pipes or hoses 34, 38 located within the protective pipes 40 arecompletely shielded from external loads.

1. A device for use in a fluid producing, underground well (1) having aninflow portion (2, 4, 6), said device comprising: a perforated, mainpipe (12) suitable for insertion into the inflow portion of the well; astrainer comprising a pervious outer mantle (16) surrounding said mainpipe; a plurality of axially extending spacer means (18) spaced about anexternal periphery of said main pipe and arranged to support thestrainer mantle (16) on said main pipe, said spacer means formingchannels (20) between the spacer means in an annular space defined bythe strainer mantle (16) and the main pipe (12); and a hydraulic pipeextending through at least one of said channels and between the spacersand coupled to an actuator (36) located proximate the inflow portion,the hydraulic pipe providing the actuator (36) with energy; wherein saidspacer means comprises a plurality of axially extending spacer strips(18).